1. Field of the Invention
Aspects of the present invention relate to an electrolyte for a lithium ion secondary battery and a lithium ion secondary battery comprising the same. More particularly, the present invention relates to a multi-layered structure electrolyte including a gel polymer electrolyte on opposite surfaces of a ceramic solid electrolyte, for a lithium ion secondary battery including positive and negative electrodes capable of intercalating/deintercalating lithium ions, and a lithium ion secondary battery including the electrode.
2. Description of the Related Art
Recently, with the development of portable devices such as cellular phones, camcorders, or notebook computers and increasing demand for slim and lightweight of the portable devices, there has been an increasing demand for high capacity, long cycle life and high stability of the lithium ion secondary battery. In addition, much attention is being paid to electric vehicles and lithium ion secondary batteries are drawing attention as power sources for electric vehicles.
A lithium ion secondary battery generally includes a positive electrode, a negative electrode, a separator for preventing a physical contact between the positive electrode and negative electrodes, and an electrolyte for transmitting lithium ions. The lithium ion secondary battery generates electrical energy by electrochemical oxidation and reduction.
In the lithium ion secondary battery, a liquid electrolyte is generally used as a medium of transferring ions of the positive and negative electrodes. However, the liquid electrolyte has a high probability of deformation or explosion due to liquid leakage or use of a combustible material and is unstable at high temperature due to use of a volatile solvent.
Therefore, recently, use of a solid electrolyte, instead of the liquid electrolyte, is under investigation. As an incombustible material, which is highly stable and nonvolatile, is used for the solid electrolyte, the solid electrolyte is stable at high temperature. In addition, since the solid electrolyte serves as a separator, the separator is not required, unlike in the conventional solid electrolyte, enabling a thin film formation process.
However, the conventional solid electrolyte has high interface resistance due to a point contact between an electrode and the solid electrolyte, low ion conductivity and lowered flexibility, making it difficult to be applied to a role to role process.